Starting device for free piston engines



March 9 9- R. PATERA5-EE$ARA 2,463,051

STARTING DEVICE FOR FREE PISTON ENGINE) Filed July 3, 1945 5 Sheets-Sheet}.

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. INVENTOR Raul msfks'o' BY I, W M

ATTORNEYS March 1, 1949. R; PATERAS PESCARA 2,463,051

STARTING DEVICE FOR FREE PIS'i'ON ENGINES Filed July 3, 1945 '5 sheets-sheet 2 Fig. 3

2 & 5:

o I INVENTUR v Patezas BY WZAMW M ATTO RN EYS March 1, 1949. R. PATERAS PESCARA STARTING DEVICEFOR FREE PIS TON ENGINES 5 Sheets-Sheet 3 Filed July .3, 1945 & x

I INVENTDR Baum, Rm

BY J MW/M ATTORNEYS March 1, 1949. R. PATERAS PEsARA STARTING DEV ICE FOR FREE PISTON ENGINES Filed July 3, 1945 I 5 Sheets-Sheet 4 INVENTDR M m 1tavra ATTORNEYS March I, 1949. R, PATERAS PEscA RA 2,463,051

I STARTING DEVICE FOR FREE PISTON ENGINES Filed July 3,1945 5 Sheets- Sheet 5 INVENTUR Itzterw ATTORNEYS Patented Mar. 1, 1949 UNITED srATEs- PATENT FFlCE STARTING DEVICE FOR FREE PISTON ENGINES Raul Pateras Pescara, Lisbon, Portugal Application July 3, 1945, Serial No. 603,060

. In France August 18, 1942 18 Claims. (01. 60-13) a which air for scavenging purposes and for replenishing the power cylinder is compressed by the engine itself, the gases under pressure comprising the excess of said air and the combustion gases which leave the power cylinder before complete expansion.

A first object of my invention is to provide a power gas generator of the kind above referred to with air compression during the return stroke of the free power piston or pistons, wherein before the said pistons are started, the power cylinder and preferably also the air chamber adapted to contain compressed air to feed the motor part of the said generator, are put under a pressure which is preferably equal to the desired working pressure.

Another object of my invention consists, in a power plant comprising a plurality of gas generators of the kind above-referred to, in starttrating the various requirements in power from the air cushion to return the power piston under the various loads to which the engine is submitted.

Fig. 4 shows a modification of the engine 11- lustrated in Fig. 1.

Fig. 5 illustrates in section another construction of an engine according to my invention.

Fig. 6 shows a third construction according to my invention. Y

Fig. '7 is a diagram explaining the operation of the engine according to Fig. 6.

ing one of said generators by means of gas under pressure issuing from other generators of the same plant. The piston or pistons of the generator to be started may be locked at the starting position while compressed gas is being forced into the starting cylinder, which is preferably the cylinder adapted to form spring means to ensure the return stroke of the power piston and which is therefore termed air cushion. And when the pressure of the compressed gases from the generators is deemed insufiicient, it may be increased by throttling the collector pipe leading such gases to the machines adapted to use same.

Still a. further object of my invention consists, when the starting capacity of the generators is formed by the air cushions thereof, in connecting such air cushions with each other in such a manner that compressed air from the air cushions of the running generators may be forced into the air cushion of the generator to be started while the power piston of the latter is retained by appropriate locking means. 7

My invention also relates to a method of proportioning the energy of compressed air used for starting purposes to the mean working pressure within the air chamber adapted to feed air into the power cylinder.

In the annexed drawings:

Fig. 1 is a general section of a free piston power gas generator provided with a starting device according to my invention.

Figs. 2 and 3 show two sets of diagrams illus- In Fig. 1, numeral I designates a general collector pipe adapted to receive gases under pressure from a number of power gas generators and to deliver the same to an appropriate machine of any description. Each generator comprises a power cylinder 2 with a free piston 3 operating within same and a compressor cylinder 4 cooperating with a piston 5 mechanically connected with piston 3 through a cylindrical member 6. There is also provided a pneumatic cushion i which ensures under normal conditions the return stroke of pistons 3, 5 and forms during starting a capacity into which air is forced under pressure to throw pistons 3, 5 toward the inner dead point.

The said air cushion comprises a cylinder 8 interior and coaxial to cylindrical member 6, and an elongated fixed piston 9 cooperating with cylinder 8. The said piston 9 is hollow and forms an air chamber 9a adapted to receive a determined quantity of starting air, this chamber communicating with cylinder 8 through an open- .ing 9b. In normal operation chamber 9a forms a part of the air cushion.

The compressor cylinder 4 is provided with inlet valves to opening to the atmosphere and with outlet valves 4b and 4c, the first one discharging compressed air into a casing l0 while the second one discharges into another casing Illa disposed in opposed relation with respect to casing ill with which it is connected by on outer pipe ll.

Power cylinder 2 is provided with air inlet ports 2a, opening in casing l0, and with outlet ports 2b which are connected with the aforedescribed collector pipe I by a branch pipe l2. Cylinder 2 is also provided with a fuel injection nozzle [3 fed by a pump I 3a actuated by a rod 5a carried by piston 5 and passing through one end cover of cylinder 4. V

Power for starting the engine is derived from a compressed air tank ll the internal pressure P of which is indicated by a pressure-gauge Ila.

Tank I4 communicates with chamber 9a through a pipe l5 provided with a. cook or valve lia.

The device adapted to control starting comprises, in a'known manner, a valve 2| to close opening 9b provided between cushion l and chamber 9a, said valve being submitted to the action of a piston 2la fixed to the stem thereof and adapted to slide within a cylindrical chamer 22 disposed at the end of chamber 911 op- ,posed to opening 9!). The aforesaid tube l5 opens into chamber 22 below piston Ma. The

latter is urged upwardly by a spring 22a and it is provided with a non-retum valve 90 adapted to permit air admission from chamber 22 into chamber 9a.

The starting control device also comprises a three-way valve or cook lib interposed on said tube l5, whereby chamber 22 may be separated from tank 14 and connected with the atmosphere. Piston 2: is then actuated against spring 22a by air pressure within chamber 9a, whereby valve 2| is opened and air is admitted into the air cushion space I, thus projecting piston 3 towards the end of cylinder 2.

In order to ensure a convenient starting position for pistons 2 and 5, there is provided a movable abutment 23 in the bottom of cylinder 4, said abutment being fixed to a piston 23a of appropriate section slidable within an auxiliary cylinder 24 preferably disposed in casing Ina. The lower end of cylinder 24 is connected with chamber 22 by a pipe 24a, whereby air pressure within said chamber may act on the lower face of piston 23a While the upper face thereof receives the action of a spring 23b and of air pressure within said casingi'lia, said pressure being admitted by a passage 26b laterally provided in the upper part of cylinder 24. It will be ,understood that when chamber 22 is connected with the atmosphere, spring 23b returns piston 28a to its lowermost position, abutment 23 then being inoperative.

The generator also comprises a valve l6 adapted to close branch pipe l2 in order to disconnect the engine from collector I during standstill periods. Valve I6 is controlled by a piston 16a. slidable within a cylinder 16b. Piston l6a is acted upon in the direction corresponding to the closure of valve 16 by air pressure from tank It through a pipe i'6c embodying a threeway controlling valve or cock lBd, whereby cylinder I61) may be connected either with pipe lie or with the atmosphere. There is also laterally provided in cylinder lBb a tube Hie connected with chamber 9a and so disposed that as soon as valve i6 is disengaged from its seat air pressure from said chamber is admitted in the end of cylinder Hib opposed to pipe i6c, whereby valve [6 is fully opened. And a spring 16 is also arranged to close valve I6 when the engine is stopped and when chamber 9a has been discharged by means of an appropriate blow-down valve la.

An exhaust pot 34 is preferably provided on tube [2 between cylinder 2 and valve i6, said pot comprising a safety valve 34a arranged to dis-' charge into the atmosphere.

With the known arrangements an engine of the kind referred to was started in the following way: Cylinder 2 and the compressed air space corresponding to casings l0 and Illa being at atmospheric pressure, air under pressure from tank M was admitted into the air cushion I to project piston 3 upwardly. During the first engine strokes pressure gradually increased in the air space H), I'M, in the collector pipe I and-in the gas reservoir generally provided between said pipe and the machine adapted to receive the gases. This method entails a number of drawbacks such as the risk of contact between the. piston and the cylinder head (or between the pistons themselves in the case of opposed piston engines), the difliculty of starting a cold engine, the loss of time necessary to reach the proper pressure in the case of a group of generators, and in certain cases the insuilicient weight of air in the power cylinder during thefirst strokes.

These inconveniences are practicallyavoided according to my invention by bringing the power cylinder 2 and the compressed air space H), Ilia.

to apressure higher than atmospheric and preferably substantially equal to the normal operating pressure pm within air spaces 10, 10a (or within collector pipe I, both pressures being substantially equal).

This may be obtained in one of the following ways:

Air from tank ll may be admitted into the compressed air-space l0, Ilia through a pressurereducing valve i'la, the latter being adjusted until the desired pressure is attained, which is ascertained by means of a pressure gauge llb. Casing i0 besides communicates with cylinder 2 through a pipe l8- of small cross-section provided with a non-return valve l9 adapted to permit flow of air into cylinder 2, to bring piston 3 to its lowermost position (-when it is at such a position that ports 2a. are closed).

This first method, wherein compressed air is derived from tank l6, may be applied in the case of but one generator as well as in the case of a group of generators for starting the first one. But when some generators of such a group have been started, air under pressure may be derived from the air spaces ll), lfla of these generators to start the other ones.

For this purpose there is provided a common pipe 35 which communicates with the compressed air spaces In of all of the generators of the group through connecting pipes 35a provided with valves 35b whereby any generator may be at will either connected to or cut off from pipe 35.

It is of advantage, before starting a generator, to open valve 35b during a certain time to warm up the engine parts'by means of the hot air from pipe 35. This warming up is particularly efflcient when valve I6 is simultaneously open, since air flows from pipe 35 to pipe I.

The above method according to which casing Ill and cylinder rare brought, before starting, to a pressure substantially equal to the mean working pressure which may vary within relatively wide limits, necessitates means to adapt the starting power to the different pressures which may prevail within said casing and cylinder.

Fig. 2 illustrates a set of diagrams which gives, with the piston stroke in abscissae:

In A the diagrams of air-pressure in cylinder 4 above piston 5 (i. e. in the space wherein compression takes place during the return stroke);

In B the diagrams of compression within cylinder 2;

And in C the diagrams of pressure in the air cushion.

In part A, curve abc corresponds to compression within cylinder 4 when the exhaust pressure of the scavenging compressor, which is practically the same as the generator working pressure, is equal to pmi. Curve aef corresponds to an exhaust pressure equal to pmz. Since the return stroke of a free piston engine decreases when the working pressure increases, curve aef is somewhat shorter than curve abc; but nevertheless the compression work for pressure pm: is much higher than for pressure mm.

Diagrams 3 also show thatthe compression work within cylinder 2 is higher for pressure mm than for pressure mm.

Therefore, for starting the engine, 'the air cushion has to deliver a work equal to the area hilcl (Fig. 2, part C, when the working pressure is equal to 221m, Whereas this work'becom'es equal to area hmno when the working pressure becomes pmz.

In order to adapt the starting energy produced by the air cushion to the actual working pressure prevailing in the compressed air space and in the power cylinder, it is possible to act either on the air volume of the air cushion, or on the pressure p. of the air introduced into the same (i. e. of the air ensuring starting), or on the starter efllciency, or on a number of these factors.

The control of the starter energy ispreferably effected by the working pressure pm.

Theadjustment of pressure in the air cushion is obtained by a throttling spindle 25 inserted in pipe l5 and actuated by a piston 25a slidable within a cylinder 26. The end of cylinder 26 opposed to spindle 25 issubmitted to the starter pressure p1 .while the other end is submitted to the working pressure respectively by means of a connecting pipe 261: connected with pipe 15 between spindle 25 and valve l5b, and by means of a pipe 26b connected with casing It. This device is so arranged that pressure in increases with pressure pm, and there isprovided a spring 25b which tends to open spindle 25.

The volume of the air cushion is adjusted by means of a capacity 21 with which it is connected by means of a conduit 28. Capacity 21 is formed as a cylinder and is provided with a piston 21a i forming an adjustable partition therein, the position of piston 21a being controlled by an abutment 29. The latter is in turn a controlled by a piston 30 slidable within a cylinder 30a under the opposed actions of pressure pm (derived from pipe H) and of a spring 30b. Piston 3U actuates a rack 3| which coacts with a gear 3|a forming a nut on a threaded rod 29a carrying abutment 29. Rotation of rod 29a is prevented by its square outer end being slidably engaged through a square hole in the fixed support of said rod. This device is so arranged that the volume of the air cushion increases with pressure pm.

Control of the starter energy by means of the air cushion eiliciency is ensured by throttling the air flow during expansion, preferably by means of a slide valve 32 actuated by a springloaded piston 32a disposed within a cylinder 32b and acted upon by pressure pm as in the case of piston 30. There is provided a cock or valve 33 by means of which cylinder 32b may be cut oil from pressure pm. i

In the case of Fig. 1 the three controlling arrangements are simultaneously applied to adapt the air cushion energy to the various pressures liable to prevail within casing I 0 and cylinder 2. But it will be understood that in some cases one arrangement or combination of two may be suflicient for the result desired. I

It will be noted that the reduction in efiiciency obtained by means of slide valve 32 is also of interestwhen the power piston is started from a position beyond its normal dead points. In such a case this reduction takes place only during the first return .stroke(starting stroke) andithas for its eiiect to decrease the startingwbrk effected by the air introduced during starting tofill the air cushion to the normal .working pressure;

According to a modification of my invention. it is possible to reduce, or even to suppress. start ing energy variations corresponding to the variable pressure prevailing within casing l0 and cylinder 2. before starting, by adjusting infaccordance with said pressure the weight of the air to be compressed in the compressor space during the return stroke. This adjustment may be eifected by decompressing the said space to an extent which increases when the said pressure increases.

-In Fig- 2, part A, I designates the pressure curve obtained by appropriately decompressing the compressor space on the upper face of piston 5, when the working pressure in casing i0 is equal to pmi, while curve II corresponds to the decompression when the working pressure is pmz. These two curves show that the compression work is lower in the second case than in the first one. This difierence may be such that it compensates the increase in compression work within the power cylinder when the working pressure increases from pm; to mm, as shown in Fig. 2, part B. The starting energy to be delivered by the air cushion ma thus remain sub stantially constant irrespective of working pressure variations within casing l0 and cylinder 2. Any adjustment in the starter energy may thus be dispensed with.

Of course, when the decompression reaches a high value for high working pressures, it may happen that the air volume forced from the compressor space into casing l0 may become negligible. In such a case cylinder scavenging must be ensured in another way, for instance by means of another generator already in operation.

Fig. 4 shows a decompressing device by means of which pressure curves such as I andII (Fig. 2, part A) may be obtained.

This figure partially illustrates in cross-section a compressor cylinder 5| provided with inlet valves Sla, three in number, for instance (two only are shown). These valves are used as decompressors. Each co-operates with a pusher rod 52 carried by a piston 52a movable within a cylinder 52b fixed to an inlet jacket surrounding cylinder 5|. Pistons 52a are actuated by submitting their outer faces to air pressure by means of a pipe 53 and they are loaded by springs 520 which tend to bring them back to their inactive position.

The degree of decompression must be adapted to the pressure prevailing in casing in and in cylinder 2 (Fig. 1), i. e. to working pressure pm.

For this purpose there is provided in the first place a controlling device 54 (Fig. 4) embodying a slide 54a adapted to bring into operation a number ofpistons 52a increasing with pressure pm, and slide 54a is actuated by a piston 54b submitted to the opposed actions of pressure pm, admitted into the corresponding cylinder by a pipe 540 communicating with casing ID of Fig. 1, and of a loading spring 5411. When pressure pm increases, slide 53a is raised and the number of inlet valves which are prevented from closing also increases.

Pressure pm is introduced into device 54 througha three-wayvalve or cock 58 disposed between the-air tank, not shown, and said device and adapted to connect said device either to said air tank or to the atmosphere.

When, decompression is to be suppressed, air

is liberated from cylinders 52b by means of valve 66, but it is of advantage that, when the engine is started, the change from decompressing to normal working should be progressive. This change may be controlled either by the time itself, or by the mean pressure within the air cushion, which pressure is itself adjusted in accordance with the "generator working pressure.

For controlling the said change as a function of time, there is inserted in the pipe 63 connecting a cylinder 52b with controlling device 54,v an adjustable throttling spindle 65 which sure of the air cushion (not shown) by means of a pipe 56a. The device is so arranged that both pressures tend to open spindle 55?) against the action of a returning spring 56b. And there is provided a by-pass tube 51, of reduced crosssection, which permits pressure to actuate piston 52a before the engine is started, when spindle 55b isclosed. This tube 51 is too small to cause an appreciable air flow during the change from decompressing to normal working. I

In the case illustrated by pressure curves I and II, Fig. 2, part A, the decompression valves are lifted during the whole return stroke, but the desired result may also be obtained by appropriately timing the beginning of compression in the compressor space, for instance by means of parts which are closed only after a given part of the return stroke, thus allowing a variable quantity of air to escape into the atmosphere. Fig. 3, parts A, B and C, refer to' such a method.

In part A, curve corresponds to air pressure within the compressor space when the working pressure pm is substantially equal to atmospheric. The area comprised between curve 0 and the horizontal axis correspondin to atmospheric pressure therefore represents the compression energy absorbed in the compressor space. Similarly, curve 11' corresponds to the working 'pressure mm and the area between II and the said horizontal axis is the energy absorbed in this case, it being observed that the beginning of compression has been delayed.

In part B, curves mm and pmz represent air pressure within the power cylinder and the hatched areas. are the corresponding energies absorbed.

It will be understood that by an appropriate timing of the beginning of compression, the sum of energies absorbed within the compressor space and the power cylinder may be kept'substantially constant, irrespective of working pressure variations, 1. e. the energy delivered by the air cushion during starting is also constant. Curves O" and II", part C, illustrate air pressure within the air cushion respectively for a working pressure equal to atmospheric or to pmz, and the areas between the curves and the axis corresponding to'atmospheric represents the energy delivered, which is substantially constant.

In a power plant comprising a plurality of gas generatorswhich may individually be put in operation, starting may be effected by compressed gas from the air cushion of one of the runnin engines. For this purpose, the air cushion of the engine to be started is connected with the air cushion of the engine or engines in operation when pressure in this. last-named air cushion is equal or higher than the pressure required in the air-cushion of the engine to .be started, for ensuring starting. Of course, the pistons of the engine to be started should be previously brought to the proper starting position.

Fig. 5 shows a plant comprising two generators one of which is to be started as above explained.

Each generator comprises a power cylinder 36 co-operating with a piston 31a connected through an extension 31 with a piston 31b dividing the corresponding cylinder into two chambers 36a and 38b, the first one acting as a scavenging compressor, while the second forms an air cushion. Chamber 38a is provided with an inlet valve 39 opening to atmosphere and with an outlet valve 40 communicating with a casing 4l surrounding cylinder 36 and connected therewith through inlet ports 4la, Cylinder 36 is formed with exhaust ports 42a through which it is connected with a collector pipe '43 adapted to receive the gases produced, by means of a connecting pipe 42 provided with a valve 42b. There is also arranged an injection pump 44 actuated by" a rod 310 fixed'to piston 31b.

In order to permit creating pressurewithin casing 4i and cylinder 38 of the generator to be started, there is provided a compressed air line 48 connected with the respective casings by means of pipes 4 lb provided with valves 4 lo.

The air cushion operates, in a manner per so well known, in such a way that its lowest and highest pressures are respectively below and above the mean working pressure of the corresponding generator. Itis thus possible, when the air cushion pressure is higher than the working pressure within casing 4|, to let some air flow from the cushion into the casing and, inversely, when the working pressure exceeds air pressure in the air cushion, to admit air from the casing into the air cushion. This adjustment is effected by the device generally referenced A inFig. 5.

Device A is interposed in a pipe 380 connecting the air cushion 38b with the pipe 4lb itself connectedwitli casing 4i as through valve Me. The said device comprises a piston valve 50 and it is connected with pipe 4lb by'means of two conduits provided with automatic non-return valves 50a and 50b in opposed respective relation, the former permitting air flow from pipe 4lb into device A and the second one from device A into pipe 4lb. Piston valve 50 is actuated by a piston 500 the lower face of which is submitted to the working pressure pm through a pipe 50c communicating with pipe 4lb, while its upper face is submitted to the mean pressure of the air cushion by means of a pipe 38h of small crosssection. Piston 500 is moreover loaded by a spring 56d acting against the mean air cushion pressure.

tons tie and 31b in thestarting position when the air cushion is being filled by compressed air. This locking device may comprise a transversely movable locking finger 44 passed through the wall of cylinder 380-381) to co-act with piston 31b. The free end of finger 44 is cut obliquely to permit downward motion of piston 31b. The opposed end is fixed to a piston 45 within a cylinder 46. Piston 45 is urged outwardly by a spring 45a and inwardly by air pressure from a tank 4'! communicating with cylinder 46 through apipe 41a provided with a three-way cock or valve 41b permitting to connect cylinder 46 either with tank 41 or with the atmosphere. In the first case pressure from tank 41 forces finger 44 inwardly against spring 45a; in the second case spring 45a returns finger 44 outwardly.-

In order to fill the air-cushion 38b of the generator to be started from the air-cushion of the generators in operation, there is provided a second common pipe 49 to which each air-cushion 38b is connected by a branch pipe 38) comprising a slide valve 31 attached to pistons 31a, 31b and so disposed that it is open when the pistons .are at their starting position. A cook or valve 38a is interposed on each branch pipe 38 Relief valves 38c permit the avoiding of any pressure rise in the compressor chamber 38a due to piston leaks when the air cushion is being filled,

The operation is as follows:

It will be supposed that the generator to be started is the left one. Before starting, the operator closes valve 38d and admits compressed air from pipe 4ib into casing 4i, whereby pistons 31a and 31b are lowered and locked by finger 44 protruding inwardly under the action of pressure from tank 41. In this position, slide-valve 31f connects the air-cushion chamber 38b with pipe 49 in which air pressure is equal to air cushion pressure within the generators in operation when their slide valves 31f are open.

The pressures within the generator to be started are then respectively equal to those cor,- responding to normal operation. It is thereforesuflicient to close valve 38c and to unlock piston by the cross-hatched area for pressume mm).

is directly connected with pipe 48 by means of a pipe 38h provided with a cook or valve 38f. Valve 38d of Fig. 5 is preferablydispensed with, as shown. Collector pipe 43 is provided with a throttling valve 43a actuated by means of a lever 43b and a pressure gauge 430 is disposed in front of valve 43.

The generator is started as follows:

As in the case of Fig. 5, casing 4| and cylinder 36 are filled with compressed air from pipe 48,

and piston 31b is locked at the starting position. The air cushion is then filled with compressed 1 gas from pipe 48, but after the pressure within 31b by turning valve 41b to connect cylinder 46 to atmosphere. The generator is thus started under running conditions. Valve 38d isthereafter opened to permit automatic air adjustment a sam a. .?...P.rmeats device A.

According to a modification of my invention, in a plant comprising a plurality of generators, starting of one of them is ensured by gases under pressure from the running generators. For this purpose, the pressure in the air cushion should be such that it oscillates between a value above the working pressure pm and a value below same.

The piston of the generator to be started is locked at the position forwhich the air cushion pressure should be equal to pm and the air cushion of the said generator is then connected with an air tank containing air at the said pressure pm, and the generator is thereafter started by merely unlocking the piston.

This method is however objectionable when the working pressure is low. Fig. 7 illustrates pressure curves di and d2 of an air cushion corresponding to working pressures mm and pm. It will be remarked that with the lower pressure pmi the position 0 of the piston is such that the energy available in the cushion (represented by the area hatched by vertical lines) is lower than the energy necessary for starting (represented collector pipe 43 has been increased, if necessary, by means of throttle valve 43a. Piston 31b is thereafter unlocked.

I claim:

1. In a free piston engine such as a power gas generator, a two-stroke internal combustion power'cylinder, a compressed air space adapted to feed air under pressure into said internal combustion power cylinder, means to force air into said compressed air space during operation of said engine, and means operative before said engine is started to bring said internal combustion power cylinder and said compressed air space to a pressure at least substantially equal to the lowest mean working pressure to prevail within said compressed air space when the engine is in operation.

2. In a free piston engine such as a power gas generator, a two-stroke internal combustion power cylinder, a power piston movable therein,

a compressed 'air space adaptedto feed air under pressure into said internal combustion power cylinder, means to force air into said compressed air space during operation of said engine, means responsive to said piston to control air flow from said compressed air space into said internal combustion power cylinder, an air canal between said compressed air space and said internal combustion power cylinder to permit air from said compressed air space to penetrate into said internal combustion power cylinder when said piston is in 'such a position that said last-named means are closed, non-return means to prevent back flow of gas through said air canal from said internal combustion power cylinder into said compressed air space, and means operative before said engine is started to bring said compressed airspace and said internal combustion power cylinder to a pressure at least substantially equal to the lowest mean working pressure to prevail within said compressed air space when the engine is in operation. v

3. In a free piston engine such as a power gas generator, a two-stroke internal combustion power cylinder, a power piston. movable therein, a gas cushion adapted to eiiect return stroke of said power piston, a compressed air space adapted to feed air under pressure into said internal combustion power cylinder, means to force air into said compressed air space during operation of said engine, means operative before said engine is started to bring said compressed air space and said internal combustion power cylinder to a pressure at least substantially equal to the lowest mean working pressure to prevail within said compressed airspace when the engine is in operation, means to force compressed gas into said air cushion to start said engine, a movable abutment adapted to limit movement of said power piston under the action of pressure within said compressed air space and said internal combustion power cylinder, means responsive to compressed gas admission into said gas cushion to press said abutment into operative position, and spring means to return said abutment to inoperative position when said engine is started.

4. In a power plant comprising a plurality of free piston power gas generators, a common collector pipe to receive gas under pressure from said generators, and each of said generators embodying a two-stroke internal combustion power cylinder having inlet and outlet ports, a compressed air space adapted to feed air under pressure into said power cylinder through said inlet ports. means to force air into said compressed air space when saidgenerator is in operation, means operative before said generator is started to bring said internal combustion power cylinder and-said compressed air space to a pressure substantially equal to the mean working pressure to prevail within said compressed air space when said generator is in operation, an individual branch pipe connecting said outlet ports with said common collector pipe, and valve means on said branch pipe. 1

5. In a power plant as claimed in claim 4, an exhaust pot on each of said branch pipes between said outlet ports and said valve means, and safety valve means on each of said exhaust pots.

6. A power plant as claimed in claim 4, in which the means operative before the generator is started to bring the internal power cylinder and the compressed air space to a pressure substantially equal to the mean working pressure to prevail within said compressed air space when said generator is in operation include a common. connecting pipe, a branch pipe between each one of said compressed air spaces and said connecting pipe, and valve means on said last-named branch pipe.

7. In a free piston engine such as a power gas generator, a two-stroke internal combustion power cylinder, a power piston movable therein, a compressed air space adapted to feed air under pressure into said power cylinder, a gas cushion to ensure return stroke of said power piston, a compressor piston mechanically'connected with said power piston to reciprocate in unison therewlth, a compressor cylinder within which said compressor piston is movable, valve means comprising inlet and outlet valves co-acting with said compressor cylinder to cause'same to force compressed air into said compressed air space during return stroke of said power piston, means operative before said engine is started to bring said power cylinderand said compressed air space to a pressure at least substantially equal to the lowest mean pressure to prevail within said compressed air space when the engine is in operation, means to force compressed gas into said gascushion to start said engine, and means to keep-at least some of said inlet valves open during the return stroke of said power piston.

8. In a free piston engine as claimed in claim '7, said last-named means being adapted to propor-, tion the number of inlet valves that are kept and means for automatically opened during the return stroke of the power piston to the pressure within said compressed air space.

9. In a free piston engine as claimed in claim 7, said last-named means being adapted automatically to allow said inlet valves to close during the return stroke of said power piston a certain time after the starting oi said engine depending upon the mean pressure within said compressed air space.

10. In a power plant comprising a plurality of power gas generators of the free piston two-stroke type embodying a movable power piston and an air cushion to ensure return stroke of said power piston, a manifold, branch pipes individually connecting said manifold with the air cushions of said generators, a valve in each of. said branch pipes, said valve being mechanically connected with said power piston to open the corresponding branch pipe only when said power piston is at a position substantially corresponding to the beginning of its return stroke, means to lock said power piston at said position, and means to control said locking means.

11. In a power gas generator, a two-stroke in ternal combustion engine unit including a power cylinder and a power piston ireely'movable in said cylinder, a compressed air space adapted to feed air under pressure to said cylinder, means to force air into said compressed air space during operation of said engine, means operative prior to the starting of said engine to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowestmean working pressure to prevail in said compressed air space when the engine is in operation, means for supplying starting energy to said piston and means for automatically adjusting said starting energy to the value of the pressure established in said power cylinder prlorto the starting of said engine.

12. In a power gas generator, a two-stroke internal combustion engine unit including apower cylinder and a power piston freely movable in said cylinder, a compressed air space adapted to feed air under pressure to said cylinder, means to force air into said compressed air space during operation of said engine, means operative prior to the starting or said engine to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowest mean working pressure to prevail in said compressed air space when the engine is in operation, means forming a gas cushion to ensure the return strokes of said piston, said gas cushion being adapted to be used for starting said engine,

adjusting the volume of said gas cushion to the value of the pressure established in said power cylinder prior to the starting of the engine.

13. In a power gas generator, a two-stroke internal combustion engine unit including a power cylinder and a power piston freely movable in said cylinder, a compressed air space adapted to feed air under pressure to said cylinder, means to force air into said compressed air space during operation of said engine, means operative prior to the starting of said engine to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowest mean working pressure to prevail in said compressed air space when the engine is in operation, means forming a gas cushion to ensure the return strokes of said piston, said gas cushion being adapted to be used for starting said engine,

and means for throttling the flow of gas inside said cushion in accordance with the value of the pressure established in said power cylinder prior to the starting of said engine to vary the efficiency of said gas cushion in proportion to said pressure value.

14. In a power gas generator, a two-stroke internal combustion engine unit including a power cylinder and a power piston freely movable in said cylinder, a compressed air space adapted to feed air under pressure to said cylinder, means to force air into said compressed air space during operation of said engine, means operative prior to the startin of said engine to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowest mean working pressure to prevail in said com pressed air space when the engine is in operation, means for supplying starting energy to said piston, a compressor combined with said power piston and operative thereby to compress air during the return strokes of said power piston and to feed it to said compressed air space and means for automatically reducing the energy absorbed by said compressor during the starting period in accordance with the value of the pressure estab lished in said power cylinder prior to the starting of said engine.

15. In a power plant including a plurality of power gas generators of the free piston type, each generator comprising a two-stroke internal combustion engine power cylinder, a power piston movable in said cylinder, a gas cushion to ensure the return strokes of said power piston, a common collector pipe to receive gases under pressure from said generators, throttle means at the outlet of said common collector pipefor artificially increasing the delivery pressure in said pipe, releasable means for locking said power piston in a position corresponding to the beginning-of the return stroke thereof, and means for feeding said gas cushion with gas from the other compressors at a pressure proportional to the delivery pressure existing in said common collector pipe.

16. In a power plant including a plurality of power gas generators of thefree piston type, each generator comprising a two-stroke internal combustion engine power cylinder, a power. piston movable in said cylinder, a compressed air space adapted to feed air under pressure to said cylinder, means to force air into said compressed air space during operation of said generator, means operative prior to the starting of said generator to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowest mean working pressure to prevail in said compressed air space when the generator is in operation, a gas cushion to ensure the return strokes of said power piston, a common collector pipe to receive gases under pressure from said generators, throttle means at the outlet 01' said common collector pipe for artificially increasing the delivery pressure in said pipe, releasable means for locking said power piston in a position corresponding to the beginning of the return stroke thereof, and means for feeding said gas cushion with gas from the other compressors at a pressure proportional to the delivery pressure existing in said common collector pipe.

17. In a power plant including a plurality of power gas generators of the free piston type,'each generator comprising a two stroke internal combustion engine power cylinder, a power piston movable in said cylinder, a compressed air space adapted to feed air under pressure to said cylinder, means to force air into said compressed air space during operation of said generator, means operative prior to the starting of said generator to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowestmean working pressure to prevail in said compressed air space when the generator is in operation, a gas cushion to ensure the return strokes of said power piston, a common collector pipe to receive gases under pressure from said generators, throttle means at the outlet of saidcommon collector pipe for artificially increasing the delivery pressure in said pipe, releasable means for locking said power piston in a position corresponding to the beginning of the return stroke thereof, a common pipe for connecting together all the compressed air spaces of the respective generators of the plant, and valve means for connecting each of said air cushions individually with said last mentioned pipe.

18. In a power plant including a plurality of power gas generators of the free piston type, each generatorcomprising a two-stroke internal c'ombustion engine power cylinder, apower piston movable in said cylinder, a compressed airspace adapted to feed air under pressure to said cylinder, means to force air into said compressedair space during operation of said generator, means operative prior to the starting of said generator to bring said power cylinder and said compressed air space to a pressure at least substantially equal to the lowest mean working pressure to'prevail in said compressed air space when the generator is in operation, a gas cushion to ensure the return strokes of said power piston, a manifold, branch a pipes individually connecting said, manifold with the air cushions of said generators, a valve in each of said branch pipes, said valve being mechanically connected with said power pistons to open the corresponding branch pipe only when said power piston is at a position substantially corresponding to the beginning of its return stroke, means to lock said power piston at said position, and means to control said locking means.

RAUL PATERAS PESCARA.

1 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS A OTHER REFERENCES Ser. No. 418,666, Miillejans et al. (A. P. 6.).

published June 15, 1943. 

